1. Field of the Invention
In one aspect this invention relates to viscous drive couplings. In another aspect, this invention relates to overrunning clutches.
2. Description of the Prior Art
The prior art contains various mechanical overrunning clutches. The overrunning clutches presently available are generally expensive due to their complex mechanical structure. Also, the clutches are difficult to lubricate properly which shortens their life expectancy. A further problem is the mechanical clutches vulnerability to torque spikes. When a sudden increase in torque is applied to a mechanical clutch the clutch can be destroyed.
Viscous couplings provide a clutch mechanism having a simple structure. One example of a viscous coupling is shown in U.S. Pat. No. 3,329,246. This viscous shear coupling has two members wherein torque is transmitted from one member to the other member by the shear characteristics of a viscous fluid.
Basically this device and other viscous couplings are designed to transmit torque from a driven member to a nondriven member regardless of the direction the driven member rotates.
Where the clutch is used in a system which requires driving force only under certain conditions the clutch can act as a power drain. For example, if the clutch is used to transmit power from an engine to a blower it should not consume power during the starting cycle but begin to transmit power to the blower as the engine speed increases.